Making a Push Button Depth Stop for my Wen Drill Press

I've made push button releases for a few past projects. In every case they made adjusting or attaching/releasing much easier to do.  This post is about how I make one to serve as a quick setting depth stop for my benchtop Wen drill press.  This is an initial prototype. Part of what it is for is to show me if it works well.  Any flaws that show up will be noted and fixed in the following prototype.  Test, update, and test again.  

Depth Stop

My Wen benchtop drill press currently uses a knurled nut you have to spin up or down on a M12 threaded post to set a stop. Tedious. For the push button upgrade I'll need an M12 fine tap.  I ordered this one from Amazon.com:

M12 fine tap

The depth stop works by pushing a threaded section against the threaded post. Push the button in and the threads are pushed back so the post can slip through the depth stop body. Release the button and the spring pushes the thread back against the post to stop it from sliding up or down. 

To make the push button return when released I'll need a small conical compression spring. I found this one that should work at McMaster-Carr.com:

Conical Springs

A 12mm drill bit is needed to make a hole so the button can slide easily up and down the 12mm post. I ordered this one from Amazon.com: 

12mm drill bit

To drill the start hole for the tapped threads I'll need a 10.8mm drill bit. I couldn't find a 10.8mm bit, but 27/64" is very close to 10.8mm.  I already have a 27/64" bit so I'll use it instead. 

27/64ths

For the prototype depth stop parts I'll use some HDPE. I have some on hand. I've chosen HDPE for this project because it is easy to machine, and somewhat self-lubricating. 

I started with a 1" thick scrap of HDPE. Milled an area down to .75", then cut the 12mm shaft hole and outer shape. 

Depth Stop Body

I removed the bar from the CNC to tap the hole. I trimmed off the bridges using a flush trim bit in a hand held router clamped in my bench vise.

The front edge of the depth stop now needs a 5/8" wide elliptical hole, 0.7937" deep for the button.

HDPE Body

In the bottom of the 5/8" hole another smaller hole .0.42"d and 0.1288" deep is needed to center the conical hinge. For precision I clamped the depth stop body vertically to pocket those holes using my CNC. 

The button itself is the key part to make this work. I cut the elliptical button from a 1" thick HDPE block. The steps to make it included:

1.  Start by drilling the 27/64" (10.8mm) hole through the side.  My low profile vise held the HDPE blank while this hole was cut.

2. Tap the 27/64" hole with the M12-1.25tpi fine tap. 

3. Next to, and overlapping 1/2 of the tapped hole drill or pocket out a 12mm hole though the blank. There is 0.121" between the centers of the tapped hole and the 12mm hole. 

4. Flip the block up 90 degrees, then use the CNC to shape the outer end of the button and cut the ellipse perimeter from the blank. 

5. Cut the button to final length to release it from the block.  I used my compound sliding miter saw to cut it. 

I made the button and hole it slides into an elliptical shape rather than a simple cylinder. This keeps it aligned with the post. The long axis of the ellipse is horizontal. There is no width to sacrifice given the 12mm hole is cut through it. 

Once assembled this prototype works as expected. It keeps the depth stop from moving up or down when the button is not pressed in. When the button is pressed in the stop can be easily moved up or down the post. 

On my Wen drill press

The one flaw is due to the post having a flat face rather than being threaded all around.  If the post was completely threaded then the depth stop could be fine adjusted by spinning it around the post. With a flat front the threads inside the depth stop disengage when spun to the front. Keeping the depth stop button at the front provides approximately 0.05" per step adjustment. Slightly less than 1/16" (0.0625")

For Aesthetic reasons only I'll likely put a small chamfer around the top and bottom edges of this depth stop. For the next prototype I'll see if I can make one from aluminum. 

For a more useful stop a shaft with 16 threads per inch would allow 1/16" per step adjustment.  A half turn of the button would move it 1/32".  A quarter turn would allow 1/64" step precision. 

Comments and question always encouraged and appreciated.  

4D